The efficiency of an optical device (e.g., the aspects of the drive voltage or power requirement of the device) is fundamentally determined by the electro-optic materials used to construct the device. Silicon materials are more easily processed and more readily available, but are not as efficient at light emission or absorption as III-V materials. Attempts have been made to create photonic devices utilizing both materials; however, most of these attempts have been limited in that the active electro-optic components of the device are included solely in the III-V material, while silicon material is used solely for passive optical waveguiding and/or driving circuitry.
Optical devices have been formed by bonding a wafer of III-V material as an active region to silicon at a relatively low temperature. After bonding, the substrate is removed using standard photolithographic techniques on the silicon substrate. The coupling of III-V and silicon regions allows for the integration of highly efficient optical devices included in the III-V region with high speed silicon integrated circuits. Prior art methods to bond III-V and silicon regions include using spin-on glass or polymer based bonding, oxides and metals; however, these solutions are only suitable for optical devices wherein optical functionality is confined to the III-V region of the device.
For hybrid III-V/silicon optical devices wherein optical functionality occurs within both the silicon and III-V regions, prior art solutions utilize a more optically compliant layer that is the same material as the III-V substrate—e.g., an Indium Phosphide (InP) bonding layer is utilized to bond III-V regions formed on an InP substrate to silicon. These prior art bonding layers are suitable for the above described hybrid III-V/silicon optical devices, as they do not hinder the optical properties of the device at the bonded interface. However, during the final sub-process of the bonding process, the substrates must be removed by acids. These acids can etch into the bonding layer, causing imperfections to propagate at the interface of the bonded material, adversely affecting the optical mode shape and propagation loss of the hybrid optical device.
Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein. An overview of embodiments of the invention is provided below, followed by a more detailed description with reference to the drawings.